Computational Exploration of Ultra-High Current PEFC Operation with Porous Flow Field.

A comprehensive 2D+1 computational model has been developed to explore the operation of a polymer electrolyte fuel cell (PEFC) with a porous flow field, also called open metallic element (OME), in the ultra-high current density regime (>2A/cm²). The computational model has been validated to a greater extent than previously published multi-phase models, including in-Situ expenmental measurement of performance, high frequency resistance (HFR) and net water drag coefficient under a wide range of input relative humidity (RH) conditions. The combined experimental and modeling investigation found that, with the OME used as the flow field, gas phase transport of oxygen is not the limiting factor, even in the ultra-high current regime. The use of OME results in significant performance improvement compared to the conventional land-channel architecture at high current. Instead of oxygen transport limitation, however, anode dry-out limits performance, as confirmed by net water drag data from both experiment and model. With the OME architecture, diffusion flow is the dominant transport mechanism of water from the catalyst layer to the flow field, compared to capillary action and convection. Results also highlight the utility of experimentally-determined anode dry-out limits for validating multi-phase models. [ABSTRACT FROM AUTHOR]